The work proposed is designed to answer several questions regarding the effects of diabetes mellitus on the ocular surface (the corneal and conjunctival epithelium). The first is whether the corneal epithelial abnormalities associated with vitrectomy in diabetics are related to metabolic abnormalities, such as sorbitol accumulation, as has been demonstrated in other diabetic tissues. Secondly, is whether the epithelial defect formation in diabetics after vitrectomy is due to a failure of resurfacing or to a failure of cellular adhesion. The third question is whether the diabetic effects on the ocular surface can be modified by compounds such as aldose reductase inhibitors which would prevent sorbitol accumulation. We propose to study the effects of diabetes on the corneal and conjunctival epithelium by (1) biochemical analysis of diabetic tissue, including (a) measurement of glycolytic and sorbitol pathway intermediates and (b) studies of basement membrane, and (2) functional studies of epithelial healing and the influence of medications, such as aldose reductase inhibitors, on that healing.